Method of controlling the level of contamination in crude petroleum



arch M W57 c. A. Scl-IAD METHOD OF CONTROLLING THE LEVEL OFCONTAMINATION IN CRUDE PETROLEUM Filed June 17. 1965 United StatesPatent O 3,309,308 METHGD F CONTROLLING THE LEVEL CQNTAMTNATION IN CRUDEPETROLEUM Charles A. Schad, 6547 E. 27th St., Tulsa, Okla. 74129 Filed.lune 17, 1963, Ser. No. 238,139 3 Claims. (Cl. 208-178) This inventionrelates to a method of controlling the level of contamination in crudepetroleum. More particularly, the invention relates to a method ofcontrolling the level of contamination in petroleum in an automaticcustody transfer system. Still more particularly, the invention relatesto a method of controlling the level of contamination in petroleum in anautomatic custody transfer system in a manner to anticipate anapproaching unacceptable level of contamination and providing means inthe method of corrective measures to reduce the level of contaminationso as at all times to keep the level of contamination below theacceptable level and thereby maintain the automatic custody transferunit in condition for substantially continuous delivery of producedpetroleum to custody of the purchaser.

In recent years a trend has developed in the petroleum industry towardthe automatic transfer of crude petroleum from the custody of theproducer to the custody of the purchaser or pipe line company. Suchsystems are usually referred to as lease automatic custody transferunits or more briefly LACT units. Typically, such installations includethe provision of flow control means wherein crude petroleum produced inone or more leases is channeled through a probe device which measuresthe level of contamination of the produced petroleum and from thencethrough a metering system wherein the quantity of produced oil beingtransferred or sold to the purchaser or pipe line company is measuredand recorded. By agreement between the producer and the purchaser, amaximum acceptable level of contamination of the produced crudepetroleum is acceptable. When the contamination level rises above suchpredetermined acceptable level the transfer of petroleum is terminatedby automatic control means in the LACT unit. After delivery isterminated measures are undertaken to treat the unacceptable petroleumto reduce or knock-out the contaminants to reestablish an acceptablelevel.

The type of contamination most generally encountered in petroleum istermed basic or -bottom sediments and water or more -brieily BS and W.The device utilized to detect contamination is usually termed a probeand. is connected electrically .with a BS and W monitor which functionsto interpret the results electrically detected by the probe to providean electrical signal proportional to the level of contamination. ln atypical LACT unit an automatic valving system is responsive to themonitor signal so that when contamination or BS and W in the petroleumbeing transferred reaches the agreed predetermined maximum acceptablelimit, the unit, by the automatic valving system, terminates the fiow ofpetroleum through the metering system and thereby terminate delivery ofcustody of the petroleum. The automatic valving system typicallychannels the flow of petroleum through a treating system. There are twobasic means of treatment of petroleum to reduce the contaminant level.One system is to circulate the contaminated petroleum through aheater-treater system wherein, by exposing the petroleum to heat and aseparating system, water and bottom sediments are caused to be settledfrom the produced petroleum. The second common means is to injectchemicals into the petroleum which, in effect, breaks down createdemulsions so that water and bottom sediments are settled out. In mostfice modern type of LACT units provision is made so that when the`contaminated oil has been circulated sufficiently to -bring it belowthe acceptable contamination level recirculation is terminated and thevalving system automatically again channels the produced petroleumthrough the metering system and thereby reestablished continuation oftransfer of custody.

Thus, with existing LACT systems, when an unacceptable level ofcontamination is encountered the transfer of custody of petroleumautomatically ceases and a treatment or recirculation process begins andcontinues until the level of contamination is brought back to anacceptable level. This means that production time is lost while anunacceptable level of contamination is being corrected. It is animportant object of this invention to provide a method of controllingthe level of contamination in produced petroleum in a manner such thatan unacceptable level of contamination is anticipated in advance andcorrective measures taken to reduce the level of contamination before anunacceptable level is reached.

Another object of this invention is the provision of a method ofcontinuously monitoring the level of contamination of petroleum,automatically determining the level of contamination versus the totalvolume of the petroleum tested and automatically instigating correctivemeasures in proportion to the level of contamination of petroleum beingtested to reduce and thereby maintain the contamination to an acceptablelevel.

These and other objects and a better understanding of the invention maybe had by referring to the following description and claims taken inconjunction with the attached drawings which:

The gure is a diagrammatic view of a lease automatic custody transferunit including the provision of a system utilizing the method of thisinvention for controlling the level of contaminates in producedpetroleum.

Briefly this invention may be described as a method of controlling thelevel of contaminates in petroleum. More particularly, but not by way oflimitation, the invention may be described as a method of controllingthe contamination level in petroleum comprising the steps of passing thepetroleum through a contaminate detector to obtain and analog electricalmeasurements proportional to the level of contaminate contained therein,converting the analog signal thus obtained to a contaminate digitalsignal, measuring the quantity of petroleum passing through the saidcontaminate detector and generating a digital signal in proportion tothe volume thereof, inte-v grating the contaminate digital signal withthe volume digital signal to obtain a contaminate per volume digitalsignal, and treating said petroleum before said petroleum passes throughsaid contaminate detector for reduction of contamination in proportionto the said obtained contaminate per volume digital signal.

Referring now to the figure a system utilizing the method of thisinvention is diagrammatically disclosed. The invention will bedescribed, for purposes of illustration, as it is particularly appliedto a lease automatic custody transfer unit wherein the custody ofpetroleum is being transferred from the producer to a purchaser.Petroleum ows to the system from a petroleum inlet 10, such as from alease consisting of a number of wells. It is understood however that insome units the petroleum inlet pipe 10 may carry petroleum from amultiplicity of leases having intermediate storage facilities and such asystem may consist of an elaborate system for systematicallytransferring petroleum from a multiplicity of leases to provide thepetroleum in the pipe 10. For simplicity, in this description, it willbe assumed that petroleum produced from a single lease is collected andows to the system for custody transferred through pipe 10. A check valve12 is typically provided to permit petroleum to flow only in a directionfrom the lease to the system. The produced petroleum flows through aheater-treater 14 where it is subjected to increased temperature forseparation of entrained solid particles, usually referred to as bottomsediments, and water.

Through pipe 16 the produced petroleum flows out of the heater-treater14 and into a storage tank 18 which functions more or less as areservoir for produced petroleum ready to be transferred to the custodyof the purchaser, such as -a pipe line company. Pipe 20 leading from thetransfer tank to a transfer pump 22 conducts the petroleum through aprobe 24 where the level of contamination is detected. Typically, theprobe 24 is a capacitance measuring and comparing device. The amount ofcontamination entrained in petroleum is reected as a change in thedielectric constant of the petroleum which in turn is detected by thecapacitance effect of probe 24. In electrical communication with probe24 is a measuring system known as a BS Iand W monitor 26. Probe 24 andthe BS and W monitor 26 are well known items of equipment in thepetroleum industry. Briefly, the BS and W monitor 26 is basically abridge circuit device which compares the capacitance detected by probe24 against a standard to obtain an electrical analog signal indicativeof the BS and W or contaminate level of the petroleum passing throughprobe 24.

Pipe 28 conducts the petroleum out of probe 24 and into a two-Way valve30. When the system is functioning to transfer petroleum to the sellerthe valve is in the position shown, that is, petroleum ilowing throughpipe 28 Hows through the valve 30 and by way of pipe 32 to `a positivedisplacement meter 34 where the quantity of petroleum being transferredis measured and recorded. When the petroleum passes through meter 34into the outlet pipe 38 custody has been transferred to the purchaser.

This is a basic custody transfer system although it is understood thatmany embellishments may be added. A typical supplemental device notshown is a sampler which periodically draws samples to provide means fordetermining the average level of quality of product being -transferred.

As it has been previously indicated, only petroleum having a contaminatelevel below pre-agreed maximum acceptable level can be transferred tothe purchaser. The BS and W monitor 26, by electrical communication withvalve 30, functions to automatically activate valve 30 to shunt the howof petroleum away from meter 34 when a given level of contamination isdetected. When this occurs, the typical arrangement is to direct theflow of petroleum away from meter 34 and back through a pipe 40 forrecirculation and treatment to bring the contamination level of theunacceptable petroleum back to an acceptable level. Typically, therejected petroleum flowing through pipe 40 past a check valve 42, andback into heater-treater 14 where it is again subjected to the heat ofthe heater-treater for the additional removal of water and bottomsediments. In the typical LACT unit, valve 30 will remain in the rejector recycle position until the contamination level detected by probe 24and BS and W monitor 26 falls below the acceptable level at which timevalve 30 will be actuated to reestablish delivery of petroleum to thepurchaser. In the meantime, after storage tank 18 is filled, noadditional petroleum can be received through inlet pipe 1t) and, byIautomatic valve means not shown, production of petroleum ceases untilthe contamination level of the petroleum in the system is reduced to anacceptable level and delivery to the purchaser is resumed. This ofcourse means that production time is lost and the eiciency of the systemto transfer custody of the produced petroleum is reduced. This inventionprovides means to anticipate increases in the contamination level and totake corrective measures to prevent the contamination level rising to orabove the unacceptable maximum limits. This invention provides means ofinstituting corrective measures to begin reduction of the contamina1tion level in advance of the rise to an unacceptable level so thatproductivity of the lease or leases from which the petroleum is producedwill not be stopped and more effective utilization can be had of thedelivery facilities.

The first step in this invention to control the level of contaminationin petroleum consists of the addition of an analog-to-digital converteror ADC circuit 42 in electrical communication with the BS and W monitor26.

As previously described the BS and W monitor delivers, by means of abridge circuit, an analog signal indicative of the level ofcontamination detected by probe 24. The ADC circuit, a circuit wellknown to electrical engineers, converts this analog signal into adigital signal indicative of the contamination of petroleum passingthrough probe 24.

Aiiixed to the meter 34 is a digital generating device 44 whichgenerates a digital electrical signal in proportion to the quantity ofuid owing through the meter. Such a digital generating device is wellknown in the petroleum industry and consists usually of a switchmechanism or other pulse generating device actuated by counter wheelsconnected to the meter 34. Typically, the digital generating device 44may be arranged to create 100 pulses for each barrel of petroleumpassing through the meter 34.

The output of the ADC circuit 42, which provides a' digital signalproportional to the contamination level detected by probe 24, and theoutput of the volume digital generating device 44, which provides adigital signal in proportion to the quantity of fluid passing throughprobe 24, is fed to an integrating circuit 46 where the two digitalsignals are integrated to obtain a total volume contami-| nate digitaloutput signal. This output signal, taken on conductor 48, is indicativeof the contamination measured by the probe 24 as compared to the volumeof fluid flowff ing through probe 24 to indicate the actual elfectivecon'J taminate level of the fluid passing through the probe 24.

As the contamination level increases such is indicated by the electricalsignal at the output 4S of integrator 46. This electrical signal may beused in a variety of Ways. As an example, by conductor 48 and through aswitch 59 the signal may be fed to a treater temperature con trol device52. The treater temperature controldevice 52 is typically a thermostattype of device regulating the temperature to which the petroleum issubjected in the heater-treater 14. When an increasing level ofcontamination is detected by the probe 24 proportional to the quantityof iluid flowing therethrough, the output of integrator 46 on conductor43 will function to raise the heater-treater temperature to separate outmore of the BS and W contained in the petroleum as it flows through theheater-treater. This in effect, counteracts the increase in contaminatelevel to begin more intensive treating of incoming petroleum to reducethe level of contamination.

As a decreasing level of contamination is reiiected in probe 24 theoutput signal on conductor 48 from integra-I tor 46 will function bymeans of the treater temperature control device 52 to reduce thetemperature applied to the petroleum in lthe heater-treater 14. In thismanner, steps are taken to apply sufficient treatment within theheater-treater 14 to reduce the BS and W level below the agreedacceptable maximum but without exposing the petroleum passing throughthe heater-treater 14 to an I unnecessarily high temperature.

Another common means of treating petroleum to reduce the BS and W levelis by injecting chemicals into the petroleum to cause the BS and W tomore easily and effectively be removed therefrom in subsequentseparation processes. The output of integrator 46 by means of conductor48 and a switch 54, may be applied to a chemical injector 56 to vary theamount of chemical injected into the incoming petroleum. Chemicaltypically is injected through a pipe 58 having a check valve 66. Thechemical injector system 55 can be said to include noti only thechemical injector 56 but also includes pipe 58, check valve 6i) and thebalance of the portion of the fluid conducting system for removal of theBS and W by the effect of chemical action.

The provision of switches 50 and 54 provide a means Where temperatureregulation and/or lchemical injection corrective measures may be takento control the level of contamination in the produced crude petroleum.

Integrator 46 may be constructed in a variety of ways all within theknowledge of any electrical engineer familiar with integrating circuitsand may include various c-alibrating and control mechanisms.

This invention provides a method of controlling the level ofcontamination in petroleum in such a Way as to more effectively `utilizelease automatic custody control equipment so that contamination will notperiodically shut the device down and forestall t-ransfer of custody ofpetroleum while treatment is being undertaken. The method of thisinvention provides a means of m-ore efficiently utilizing leaseautomatic custody transfer systems.

Although the invention has .been described with a certain degree ofpartcula-rity it is manifest that many changes may be made in thedetails of co-nstruction and the arrangement of components withoutdeparting from the spirit and scope of this disclosure.

What is claimed: 1. A method of controlling the level of BS and W inpetroleum comprising:

passing the petroleum through a temperature controllable heater-treaterand from thence through a BS and W level detector;

generating a contaminate electrical analog signal in proportion to thelevel of BS and W;

converting the contaminate analog signal thus generated to a contaminatedigital signal; measuring the quantity of flow of petroleum passingthrough said BS and W level detector and generating a volume digitalsignal in proportion thereto;

integrating the contaminate digital signal With the volume digitalsignal to obtain a total volume contaminate digital signal;

and cont-rolling the temperature of said heater-treater in response tosaid total volume contaminate signal to increase the temperature of saidheater-treater as the level of total volume contamination increases.

6 2. A method of controlling the level of BS and W in petroleumcomprising:

passing the petroleum through a chemical injector and from thencethrough a BS and W level detector;

generating a BS and W electrical analog signal in proportion to thelevel of BS and W;

converting the contamination analog signal thus generated to acontaminate digital signal;

measuring the quantity of flow of petroleum through said BS and W leveldetector and :generating a volume digital signal in proportion thereto;

integrating the contaminate digital signal with the volume digitalsignal to obtain a total volume contaminate signal;

and controlling the quantity of BS `and W reducing chemical injectedinto said petroleum passing through said chemical injector with saidtotal volume contaminate signal.

3. A -method of controlling the BS and W level in petroleum comprising:

passing the petroleum through a BS and W detector to obtain an analogelectrical measurement proportional to the level of BS and W thereof;

converting the analog signal thus obtained to a contaminate digitalsignal;

measuring the petroleum passing through the said BS and W detector andgenerating ya volume digital signal proportional to the volume thereof;

integrating the contaminate digital signal with the volume digitalsignal to obtain a total volume contaminate digital signal;

and treating said petroleum before said petroleum passes through said BSand W detector for lreduction of BS `and W in proportion to the saidobtained total volume contaminate digital signal.

References Cited by the Examiner UNITED STATES PATENTS 3,107,526 10/1963Kuntz 73-195 3,163,173 12/1964 Kuntz 137-93 DELBERT E. GANTZ, PrimaryExaminer.

HERBERT LEVINE, Examiner.

3. A METHOD OF CONTROLLING THE BS AND W LEVEL IN PETROLEUM COMPRISING:PASSING THE PETROLEUM THROUGH A BS AND W DETECTOR TO OBTAIN AN ANALOGELECTRICAL MEASUREMENT PROPORTIONAL TO THE LEVEL OF BS AND W THEREOF;CONVERTING THE ANALOG SIGNAL THUS OBTAINED TO CONTAMINATE DIGITALSIGNAL; MEASURING THE PETROLEUM PASSING THROUGH THE SAID BS AND WDETECTOR AND GENERATING A VOLUME DIGITAL SIGNAL PROPORTIONAL TO THEVOLUME THEREOF; INTEGRATING THE CONTAMINATE DIGITAL SIGNAL WITH THEVOLUME DIGITAL SIGNAL TO OBTAIN A TOTAL VOLUME CONTAMINATE DIGITALSIGNAL; AND TREATING SAID PETROLEUM BEFORE SAID PETROLEUM PASSES THROUGHSAID BS AND W DETECTOR FOR REDUCTION OF BS AND W IN PROPORTION TO THESAID OBTAINED TOTAL VOLUME CONTAMINATE DIGITAL SIGNAL.